The present invention relates generally to an internal combustion steam engine that operates with an alcohol fuel and, in particular, to an alcohol/water fuel system for supplying a vaporized fuel to the engine. Upon combustion, superheated steam is generated within the cylinders to produce an elevated pressure and temperature. More specifically, the present invention pertains to a unique combination of internal combustion and external burner steam technologies particularly adapted for recirculation of heat energy to produce a highly efficient engine adapted for automotive, farm, and other uses.
The present invention is further directed to an improved vaporizer for use in connection with the above-described water/alcohol internal combustion steam engine. Such an engine was fully described in the prior U.S. Pat. No. 4,509,464 to the present inventor, Hansen. Therefore, the construction and operation of the engine itself will not be considered in detail herein except as it relates to the implementation of the present vaporizer.
Indeed, the earlier '464 Hansen patent relates to improved vaporizer technology, specifically, to a dual-chamber vaporizer construction adapted to minimize the adverse effects of fractional distillation. The vaporizer of the '464 patent has been found to perform satisfactorily for alcohol/water fuels down to about 90 proof, particularly where the fuel is of substantially pure quality, that is, uncontaminated by foreign solutes. In this connection, as water and alcohol are both excellent solvents, keeping the fuel free of solutes has proved to be a problem of non-trivial proportion.
This problem of solutes or fuel contamination has been found to be of substantial importance in connection with the commercial exploitation of internal combustion steam technology. Although high purity alcohol fuels are readily available, the cost of these fuels can range from twice to as much as ten times that of fuels produced under less exacting and controlled conditions.
The impact of the solutes problem is further accentuated when it is realized that many of the potential users of the alcohol-based internal combustion steam engine, e.g. farmers, are persons who have ample access to the recyclable waste or home-produced agricultural base stock from which alcohol may be produced. Such consumers, therefore, can be expected to manufacture fuel for their consumption as well as others in their locale. Fuels from such indigenous and varied sources characteristically contain higher impurity concentrations.
Even where uncontaminated fuel is available, the problems of fractional distillation again surface when operating with fuels of super-low proofage, i.e. generally below about 90 proof. For such fuels, the residual affinity of the alcohol molecules (for water) is insufficient `to bring` or capture the increasingly greater proportion of water molecules as the alcohol is vaporized. This problem is particularly acute at lower vaporizer temperatures which, as noted below, have been found to track reductions in alcohol concentrations.
It will be appreciated, therefore, that the improvements in vaporizer technology described herein are directed, first, to minimizing or totally eliminating the problems associated with fuel impurities and, second, to permitting the use of alcohol-based fuels of yet lower alcohol concentrations, for example 80 proof.
Importantly, and directly associated with obtaining this latter objective, the present invention results in yet another improvement in the overall efficiency of the internal combustion steam engine. Efficiencies of approximately 60 percent are now obtainable which, in turn, result in typical fuel economies of between 20 and 40 miles per gallon of 80 proof alcohol-based fuel--such fuel being obtainable for as little as ten cents per gallon.
The internal combustion steam engine described in the Hansen '464 patent requires no radiator as the waste heat collected in the engine's liquid cooling system is routed to the fuel vaporizer where it is converted into useful energy in the processes of vaporizing the alcohol based fuel. In this manner, one significant source of engine inefficiency, the dissipation of engine heat by the radiator, has been largely eliminated.
The Hansen '464 engine also reduced a second major source of engine inefficiency by converting the otherwise wasted exhaust gas heat energy into useful work by preheating the incoming carburetor combustion air.
As noted, certain difficulties were experienced with the engine configuration of Hansen '464 as the proofage of the fuel was reduced, that is, as the ratio of water to alcohol was increased. More specifically, it has been found that the amount of waste engine heat available in the cooling system generally decreases as the fuel proofage is reduced.
Coupled with this reduced waste heat generation is the counterproductive requirement that the fuel itself requires more heat energy to vaporize at these higher water concentrations--this by reason that water requires more energy per pound to vaporize than, for example, ethanol. Thus, even with the improved two-chamber vaporizer described in Hansen '464, fractional distillation was again found to be a problem for alcohol fuels of very low proofage.
With respect to the second source of waste engine heat discussed above, it was discovered that the exhaust gas heat energy actually increases as the fuel proofage is lowered due, principally, to the increased steam content of the engine exhaust. The available exhaust gas heat energy significantly exceeds the combustion air preheat requirement.
Unlike the vaporizer of Hansen '464, the present vaporizer has been substantially reconfigured to facilitate collection and conversion of waste heat energy from both the engine coolant and exhaust systems. In this manner the unused exhaust heat energy is meaningfully recycled thereby correcting inadequacies in vaporizer operation at lower proofages while, importantly, raising the overall efficiency of engine operation.
The vaporizer preferably defines a generally enclosed rectangular volume having a form-factor adapted to fit into, and replace, the radiator of a conventional internal combustion gas engine. More specifically, the vaporizer comprises respective air-tight `exhaust gas` and `vapor` compartments and chambers vertically separated by a `crown sheet` barrier. The lower or exhaust gas chamber has inlet/outlet ports at opposed ends thereof and interior baffles whereby the flow of exhaust gas is routed through this lower chamber in proximity to the crown sheet--such sheet defining a shared common wall between the two chambers.
Particularly significant to the performance of the present vaporizer (especially where low proofage and contaminated fuels are used) is its efficacious utilization of the excess exhaust gas energy. These exhaust gases are employed, not merely as a supplemental source of heat energy, but as an energy source at substantially greater temperature, typically between 500.degree.-600.degree. F., than available using the engine coolant approach of Hansen '464.
The vaporizer crown sheet is heated by passage of the exhaust gases to substantially the temperature of the gas itself. As discussed in more detail hereinafter, vaporization is achieved herein by spraying liquid fuel onto the crown sheet which, as noted, has been raised to a temperature several hundred degrees above the vaporization temperature of either water or alcohol (ethanol). It will be appreciated, therefore, that the fuel instantaneously vaporizes upon contacting the crown sheet without regard to the proofage or solutes contained therein.
The upper vaporization region of the Hansen '464 vaporizer, by contrast, receives the engine coolant at its hottest temperature, typically 260.degree. F.--well above the 212.degree. F. vaporization temperature of the hardest-to-vaporize fuel constituent, water. For this reason, the Hansen '464 vaporizer operated well.
Problems with this prior art vaporizer, however, are found where engine operations are attempted with alcohol fuel concentrations below about 90 proof. As previously noted, such operation is associated with a corresponding reduction in the available coolant system heat energy resulting, in turn, in lowered coolant temperatures. As coolant temperatures approach the vaporization temperature of water, fractional distillation is again seen.
The present vaporizer does not, however, sacrifice the efficiency advantages achieved through the recycling of waste engine heat. In conformity with the teachings of Hansen '464, no radiator is employed. Instead, a network of copper tubes defining a fuel preheating heat exchanger is positioned in the vapor chamber above the crown sheet through which the engine coolant is passed. Fuel is sprayed onto this heat exchanger which, in turn, lowers the coolant temperature and heats and/or vaporizes the fuel. The unvaporized fuel thereafter contacts the crown sheet where complete vaporization is assured.
A further advantage of the present vaporizer relates to its ability to handle the wide fuel vaporization demands associated with corresponding engine load changes. It will be appreciated that substantially greater vaporization is required for high vehicle speeds or uphill travel as compared with idle or low speed operations.
Accommodation of these ranging load demands is achieved through the use of a plurality of spray nozzles or injectors in the vapor chamber, each injector being gated-on in response to predetermined vapor chamber pressures. Two injectors have been found to be sufficient for most applications.
Thus, at vapor pressures in excess of about 3.5 psi all fuel spray injectors are off--the engine is operating from the residual volume of pressured fuel vapor in the vapor chamber and from any vapor being generated by the engine coolant heat exchanger. As the vapor pressure drops below about 2.5 psi, the first vapor spray injector is enabled. This injector, be placed in proximity to the hottest region of the crown sheet, ordinarily provides sufficient fuel vapor for continuing normal cruise vehicle operations. In fact, excess vaporization ordinarily will occur with this single injector resulting in the periodic shutting-off of the injector as, again, pressures in excess of 3.5 psi are achieved.
At ever increasing engine/vehicle loads, the proportion of time that the injector is "on" increases until the point is reached where the injector must remain "on" continuously to maintain sufficient operational vapor pressure. Under extreme load conditions, the vapor pressure may continue to decrease, notwithstanding that this first injector remains on continuously, thereby necessitating use of the second or auxiliary spray injector. This injector, like the first injector, is pressure controlled, being enabled when vapor chamber pressures drop below about 1.5 psi.
Advantageously the exhaust heat energy available to the vaporizer increases with increasing engine power loads thereby providing the necessary energy to vaporize the correspondingly increased fuel requirements. Crown plate temperatures remain relatively constant with changing engine loads. As a consequence, highly efficient vaporization is realized under all load conditions.
And yet a further feature of the present vaporizer relates to the highly effective sound muffling characteristics associated with engine combustion. More specifically, the exhaust gas emitted by the present engine, particularly where low proofage fuel is used (e.g. 80 proof) contains a substantial percentage of superheated steam (e.g. 40%) at temperatures of between 500.degree.-600.degree. F. As the exhaust gas passes through the vaporizer, it is significantly cooled--exiting the vaporizer at temperatures around 200.degree. F. This cooling results in significant condensation and a corresponding drop in pressure.
As a consequence, "noise" pressure waves are substantially attenuated as the exhaust transits the vapor chamber thereby eliminating or significantly reducing the need for a separate noise reduction system. And due to the inherently pure, nonpolluting character of the internal combustion steam engine, mufflers and catalytic converters may be entirely avoided.
From the foregoing it will be appreciated that the vaporizer of the present invention exhibits startling improvements in a number of important categories critical to internal combustion steam engine operation. These improvements include full and complete vaporization, i.e. the elimination of fractional distillation, under widely varying engine load conditions and where impure and low proofage fuels are employed; the increase in engine efficiency by more effectively recycling engine waste energies; the elimination or reduction in the requirement for engine muffler systems; and control over the quantity of vapor production under extreme load variations.